1. Field of the Invention
The present invention relates to a blower and it is effective when applied to a blower which supplies cooling air to a radiator and a condenser for a vehicle or the like.
2. Description of the Related Art
A blower for supplying cooling air to a radiator and a condenser for a vehicle comprises an axial flow type blade wheel for producing an air flow, an electric motor for rotating the blade wheel, a shroud which surrounds and covers the blade wheel so as to prevent air discharged from the blade wheel from being sucked again by the blade wheel, and the like.
In order to prevent the air discharged from the blade wheel from being sucked again by the blade wheel without fail, it is preferable to decrease the size of the gap between the ends of the blades of the blade wheel and the inner wall of the shroud to as small as possible.
As a heat exchanger, such as a radiator or a condenser for a vehicle, or the like, takes outside air used for cooling at higher flow rate, it is usually mounted on a front end of the vehicle, so that the blower is exposed to rain, snow, or the like together with the cooling outside air and the blade wheel and the shroud tend to be wetted with water.
After that, if the blower is stopped for a long time at night and the vehicle is not operated, water drops adhered on the surfaces of the blade wheel and the shroud fall down to be gathered and accumulated at a lower side due to gravity thereof. When the temperature of the atmosphere is low in a winter season or the like, the accumulated water drops are frozen so as to connect the top ends of the blades with the shroud. As a result, there is a problem that the blade wheel cannot rotate (hereinafter, this problem will be referred as a freezing lock).
Especially, in a case in which an annular ring, for connecting the blade top ends of the blade wheel, is installed on the blade top ends of the blade wheel, the ring and the shroud are connected by freezing along a relatively wide range of the shroud so that the lower end side of the shroud becomes the center of the range. In such a case, the freezing lock presents a troublesome problem.